The process by which the mammalian immune system recognizes and reacts to foreign or alien materials is a complex one. An important facet of the system is the T cell response. This response requires that T cells recognize and interact with complexes of cell surface molecules, referred to as human leukocyte antigens ("HLA"), or major histocompatibility complexes ("MHCs"), and peptides. The peptides are derived from larger molecules which are processed by the cells which also present the HLA/MHC molecule. See in this regard Male et al., Advanced Immunology (J. P. Lipincott Company, 1987), especially chapters 6-10. The interaction of T cell and complexes of HLA/peptide is restricted, requiring a T cell specific for a particular combination of an HLA molecule and a peptide. If a specific T cell is not present, there is no T cell response even if its partner complex is present. Similarly, there is no response if the specific complex is absent, but the T cell is present. This mechanism is involved in the immune system's response to foreign materials, in autoimmune pathologies, and in responses to cellular abnormalities. Recently, much work has focused on the mechanisms by which proteins are processed into the HLA binding peptides. See, in this regard, Barinaga, Science 257: 880 (1992); Fremont et al., Science 257: 919 (1992); Matsumura et al., Science 257: 927 (1992); Latron et al., Science 257: 964 (1992).
The mechanism by which T cells recognize cellular abnormalities has also been implicated in cancer. For example, in PCT application PCT/US92/04354, filed May 22, 1992, published on Nov. 26, 1992, and incorporated by reference, a family of genes is disclosed which are processed into peptides which, in turn, are expressed on cell surfaces, which can lead to lysis of the tumor cells by specific CTLs. The genes are said to code for "tumor rejection antigen precursors" or "TRAP" molecules, and the peptides derived therefrom are referred to as "tumor rejection antigens" or "TRAs". See Traversari et al., Immunogenetics 35: 145 (1992); van der Bruggen et al., Science 254: 1643 (1991), for further information on this family of genes. Also see U.S. Pat. No. 5,342,774, incorporated by reference.
In U.S. patent application Ser. No. 938,334, now U.S. Pat. No. 5,405,940 the disclosure of which is incorporated by reference, nonapeptides are taught which are presented by the HLA-A1 molecule. The reference teaches that, given the known specificity of particular peptides for particular HLA molecules, one should expect a particular peptide to bind one HLA molecule, but not others. This is important, because different individuals possess different HLA phenotypes. As a result, while identification of a particular peptide as being a partner for a specific HLA molecule has diagnostic and therapeutic ramifications, these are only relevant for individuals with that particular HLA phenotype. There is a need for further work in the area, because cellular abnormalities are not restricted to one particular HLA phenotype, and targeted therapy requires some knowledge of the phenotype of the abnormal cells at issue.
In U.S. patent application Ser. No. 008,446, filed Jan. 22, 1993 and incorporated by reference, the fact that the MAGE-1 expression product is processed to a second TRA is disclosed. This second TRA is presented by HLA-C*1601-molecules. The disclosure shows that a given TRAP can yield a plurality of TRAs.
In U.S. patent application Ser. No. 994,928, filed Dec. 22, 1992, and incorporated by reference herein, tyrosinase is described as a tumor rejection antigen precursor. This reference discloses that a molecule which is produced by some normal cells (e.g., melanocytes), is processed in tumor cells to yield a tumor rejection antigen that is presented by HLA-A2 molecules.
U.S. patent application Ser. No. 32,978 cited supra, reports on a nucleic acid molecule which codes for a tumor rejection antigen precursor which differs from those described previously. The TRAP of the invention described therein is processed to at least one tumor rejection antigen that is presented by HLA-A2 molecules; however sequence analysis indicated that the TRAP of the invention is not, nor is it related to, tyrosinase. Thus the invention of the parent application relates to a nucleic acid molecule which codes for a tumor rejection antigen precursor, or "TRAP" molecule. This "TRAP" molecule is not tyrosinase. Further, the TRAP of the invention of the parent application is processed to at least one tumor rejection antigen, or "TRA", which is presented by HLA-A2 molecules. The TRA is not tyrosinase related, and other TRAs derived from the TRAPs of the invention may be presented by other HLA molecules.
In a paper published after the above-identified parent application, Kawakami, et al., Proc. Natl. Acad. Sci. USA 91: 3513-3519 (1994) also identified the subject matter of the parent application as a gene coding for a melanoma antigen.
Further work shows that the gene coding for this TRAP, referred to hereafter as "Melan-A", is about 18 kilobases long, and comprises 5 exons. It appears to be expressed only in melanoma and melanocytes, thus serving as a marker for these cells.
The invention and various aspects thereof will be elaborated upon in the disclosure which follows.